| Title | Observation of a Repeated Step-wise Fracture Growth During Hydraulic Fracturing Experiment at the Grimsel Test Site |
|---|---|
| Authors | Nathan DUTLER, Benoît VALLEY, Linus VILLIGER, Valentin GISCHIG, Florian AMANN |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | hydraulic stimulation, reservoir mechanics, seismo-hydromechanical processes, stick-split mechanism, hydraulic clapping mechanism |
| Abstract | Hydraulic fracturing (HF) experiments were conducted at the Grimsel Test Site (GTS), Switzerland, with the aim to improve our understanding of the seismo-hydro-mechanical processes associated with high-pressure fluid injection in a moderately fractured crystalline rock mass. Observations from one of these HF experiments indicate simultaneous propagation of multiple fractures during continuous fluid injection. The pressure measured in one observation interval show a cyclic response indicating repeated step-wise fracture growth. This is interpreted as a stick-split mechanism propagating fractures in an episodic manner and connecting them to the natural fracture network. In addition, transient partial closure and opening of fractures on the time-scale of seconds to minutes were observed from pressure and deformation monitoring. Our data set provides unprecedented insight in the complexity of hydraulic fracture propagation. |